Resumen

LIMA-LIMA, H. et al. Análisis de reacciones en la transición de CdS (semiconductor) a CdCO₃ (aislante) en formato de películas delgadas obtenidas mediante DBQ. Superf. vacío [online]. 2008, vol.21, n.2, pp.21-26. ISSN 1665-3521.

By Chemical Bath was obtained thin films on glass-substrates with temperature interval of 80°C - 20°C. The used solution are: CdCl₂ 0.02 M, KOH 1.5 M, NH4OH 0.5 M and SC(NH₂)₂ 0.2 M, they were prepared at room temperature using deionised water. Volume of reagents, velocity of agitation and reaction temperature stayed constant. The pH of reaction was approximately 8.3. The deposit time varies with temperature. From previous results on Optic Absorption, is obtained the prohibited bandwidth, for CdS at 80°C, Eg = 2.42 eV and CdCO₃ at 20°C, Eg = 3.87 eV. By X-ray diffraction was identified the cubic phase of CdS at 80°C, with a peak located in the angular position: 2θ = [26.68] and at 20°C it observed signals at 2θ = [23.26, 30.22, 36.30, 43.8, 49.90] that correspond to CdCO₃ in rombohedral phase. In interval 40°C<T<60°C, was identified signal from both compounds. By Optic Microscopy was obtained pictures that shown the gradual transition of CdS→CdCO₃ with growth of crystal. The precursors of ions sulphur (S^-2) and carbonate (CO^-2₃) are sulphydric acid (H₂S) and carbonic acid (H₂CO₃), respectively, in according this work. Both acids come from of hydrolytic decomposition of thiourea. The influence of pH, solubility of (H₂S) and CO₂ are considered in the interval of temperature deposited, and the influence of last in the reaction.

Palabras llave : Solubility; Thin films; Carbonate ion; Coordinate complex.

        · resumen en Español     · texto en Español     · Español ( pdf )